The present invention relates to radiation-emitting devices, and more particularly, to providing better control of radiation delivery from radiation-emitting devices.
Radiation-emitting devices are generally known and used for radiation therapy in the treatment of patients, for example. Typically, a radiation therapy device includes a gantry which can be swiveled around a horizontal axis of rotation in the course of a therapeutic treatment. A linear accelerator is located in the gantry for generating a high-energy radiation beam for therapy. This high radiation beam can be an electron radiation or photon (X-ray) beam. During treatment, the radiation beam is provided on one zone of a patient lying in the isometer of gantry rotation.
The delivery of radiation by a radiation therapy device is normally prescribed and approved by an oncologist with administration by a therapist. Typical therapy involves programming the device by the therapist to deliver the radiation beam at a known and constant rate of a chosen number of monitor units per time period, (e.g., MU/minute), where a monitor unit generically refers to a dose unit of radiation for a chosen calibration. Monitoring of the total dose delivered at a chosen time interval, for example, every 10 milliseconds, determines when the total desired dosage has been provided to end the therapy. Unfortunately, the total dosage may be slightly exceeded, since a sampling point usually does not occur at a precise point of completion of the desired total dosage delivery. Even slight excesses of radiation are considered highly undesirable.
Thus, while typical therapy does provide needed radiation treatment, improvements in the process of delivering a prescribed total dose are still desirable. Accordingly, what is needed is a method and system for providing a desired total dosage with greater control and accuracy, including fractional monitor unit delivery control.
The present invention provides a method and system for achieving more accurate radiation delivery during radiation treatment by a radiation-emitting system. In a method aspect, and system for achieving same, the method includes providing a table of dose rate values for accumulated dosages in a treatment unit of the radiation emitting system, and controlling a dose rate of radiation emitted from the radiation emitting system through utilization of the table of dose rates. Controlling further includes determining an accumulated dosage at a sampling point, and comparing the accumulated dosage to a total desired dosage. The dose rate is adjusted based on the table of dose rate values and the determined accumulated dosage, with the dose rate ramped down as the accumulated dosage nears the total desired dosage. Accumulated dosages include fractional numbers of monitor units.
Through the present invention, a straightforward technique achieves more accurate control of radiation delivery without requiring significant and expensive hardware device changes and/or redesign. Further, a significantly higher resolution in the control of radiation delivery by the treatment system results from a reduction in dose rate that causes a corresponding reduction in the accumulated number of monitor units per sampling period. These and other advantages of the aspects of the present invention will be more fully understood in conjunction with the following detailed description and accompanying drawings.